Thin-film magnetic head for reducing track width, preventing write fringing and reducing magnetic saturation, and production method therefor

ABSTRACT

A track width regulating section having a track width, which is smaller than the resolution obtained by the wavelength of the light used for exposure and development of a resist, is formed between a lower core layer and an upper core layer. Since the width of the upper core layer is larger than the track width, magnetic saturation can be effectively reduced. Inclined faces are formed on the upper surface of the lower core layer so as to be inclined in directions away from the track width regulating section, thereby adequately preventing write fringing.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a thin-film magnetic recordinghead for use in, for example, a flying magnetic head, and moreparticularly, to a thin-film magnetic head which is capable of reducingthe track width, preventing write fringing, and reducing magneticsaturation, and a production method for the head.

[0003] 2. Description of the Related Art

[0004]FIG. 12 is a partial front view showing the structure of aconventional thin-film magnetic head (inductive head), and FIG. 13 is apartial sectional view of the thin-film magnetic head, taken along lineXIII-XIII in FIG. 12, as viewed from the directions of the arrows.

[0005] Referring to FIGS. 12 and 13, a lower core layer 1 is made of amagnetic material, such as permalloy, and a nonmagnetic gap layer 7 isformed thereon.

[0006] As shown in FIG. 13, a coil layer 5 is formed on the gap layer 7via an organic insulating layer 4 made of a polyimide, a resist, or thelike.

[0007] An organic insulating layer 6 made of a polyimide, a resist, orthe like is formed on the coil layer 5, and an upper core layer 3 madeof a magnetic material, such as permalloy, is formed on the organicinsulating layer 6.

[0008] As shown in FIG. 12, a leading end portion 3 a of the upper corelayer 3 opposes the lower core layer 1 via the gap layer 7, and thewidth thereof is limited to a track width Tw. A base end portion 3 b ofthe upper core layer 3 is magnetically connected to the lower core layer1.

[0009] In the inductive head shown in FIGS. 12 and 13, when a recordingcurrent is applied to the coil layer 5, a recording magnetic field isinduced in the lower core layer 1 and the upper core layer 3, and amagnetic signal is recorded on a recording medium, such as a hard disk,by a leakage magnetic field from between the leading end portion 3 a ofthe upper core layer 3 and the lower core layer 1.

[0010] With future increase in recording density, it is necessary toreduce the track width.

[0011] As described above, the track width Tw is regulated by the widthof the leading end portion 3 a of the upper core layer 3 (see FIG. 12).The upper core layer 3 is formed by so-called flame plating.

[0012] In flame plating, a resist layer is first applied over the entiresurface where the upper core layer 3 is to be formed, and a pattern ofthe upper core layer 3 is formed on the resist layer by exposure anddevelopment. Subsequently, the pattern is plated with a magneticmaterial, and the resist layer is removed, thereby finishing the uppercore layer 3 having the shape shown in FIGS. 12 and 13.

[0013] The resolution of the resist layer is greatly concerned with thewavelength of the light used for exposure and development. Theresolution can be improved by shortening the wavelength.

[0014] However, the resolution has, of course, its limits, and it isimpossible to perform patterning when the track width Tw regulated bythe width of the leading end portion 3 a of the upper core layer 3 issmaller than the resolution limit. Accordingly, it is difficult for theinductive head with the structure shown in FIGS. 12 and 13 to reduce thetrack width with future increase in recording density.

[0015] When the track width Tw is reduced, the volume of the leading endportion 3 a of the upper core layer 3 is decreased, and magneticsaturation becomes pronounced with an increase in recording frequency.This degrades the recording characteristics.

[0016] In the inductive head shown in FIGS. 12 and 13, a leakagemagnetic field produced between the lower core layer 1 and the leadingend portion 3 a of the upper core layer 3 protrudes from the track widthTw, that is, so-called write fringing is prone to occur.

[0017] When write fringing occurs, the track position on a recordingmedium cannot be detected precisely, an tracking servo error is caused,and the recording characteristics are degraded.

[0018] Write fringing is prone to be caused when the lower core layer 1protrudes from the track width Tw, as shown in FIG. 12, and the distancebetween the protruding portion of the lower core layer 1 and the leadingend portion 3 a of the upper core layer 3 is short.

[0019] Japanese Unexamined Patent Application Publication No. 10-143817discloses the structure of an inductive head which effectively preventswrite fringing described above.

[0020] However, the invention disclosed in the above publication makesthe production procedure troublesome. That is, the production procedureincludes a process of removing the portion of the gap layer 7 protrudingfrom the track width Tw shown in FIG. 12. While an appropriate distancecan be formed between the lower core layer 1 and the leading end portion3 a of the upper core layer 3 by etching the surface of the lower corelayer 1, which is exposed by removing the portion of the gap layer 7, byion milling, magnetic powders adhere to both side faces of the leadingend portion 3 a and the like. A process of removing the adhering powdersis also required.

[0021] Furthermore, the disclosed invention does not allow reduction intrack width and prevention of magnetic saturation.

SUMMARY OF THE INVENTION

[0022] The present invention solves to the above conventional problems,and an object of the present invention is to provide a thin-filmmagnetic head which is capable of reducing the track width, preventingwrite fringing, and reducing magnetic saturation, and a productionmethod for the head.

[0023] According to an aspect of the present invention, there isprovided a thin-film magnetic head including upper and lower corelayers, and a track width regulating section disposed between the upperand lower core layers so as to have a width shorter than those of theupper and lower core layers, wherein the track width regulating sectionis composed of a lower pole layer connected to the lower core layer, anupper pole layer connected to the upper core layer, and a gap layerdisposed between the lower pole layer and the upper pole layer, or iscomposed of an upper pole layer connected to the upper core layer and agap layer disposed between the upper pole layer and the lower corelayer, and an inclined face is formed on the upper surface of the lowercore layer extending on both sides of the track width regulating sectionso as to be inclined away from the track width regulating section in thetrack width direction in order to gradually increase the distance fromthe upper core layer.

[0024] As described above, the track width regulating section, whosewidth in the track width direction is regulated by the track width, isformed between the upper core layer and the lower core layer. The upperpole layer magnetically connected to the upper core layer is formed inthe track width regulating section. Since the inclined face inclined inthe direction away from the upper core layer is formed on the uppersurface of the lower core layer extending from both sides of the trackwidth regulating section, an appropriate distance is ensured between theupper pole layer and the lower core layer, and write fringing can beeffectively prevented.

[0025] The width of the upper core layer formed on the upper pole layeris larger than the track width. This adequately reduces magneticsaturation adjacent to the leading end portion of the upper core layer.

[0026] In a production method which will be described later, the widthof the track width regulating section (=the track width) can be madesmaller than the resolution obtained by the wavelength of the light usedfor exposure and development of a resist, which allows the track widthto be reduced with future increase in recording density.

[0027] Preferably, the track width to be regulated by the width of thetrack width regulating section is 0.4 μm or less. This value is smallerthan the resolution obtained when the i-line is used during exposure anddevelopment of the resist. More preferably, the track width is set at0.2 μm or less.

[0028] Preferably, an inclination angle θ1 of the inclined face formedon the upper surface of the lower core layer with respect to the trackwidth direction ranges from 2° to 10°. Within this range, it is possibleto adequately suppress write fringing and to sufficiently maintain theshielding function of the lower core layer.

[0029] According to another aspect of the present invention, there isprovided a thin-film magnetic head including upper and lower core layershaving a width larger than the track width, and a track width regulatingsection disposed between the upper and lower core layers so as to have awidth limited to the track width, wherein the track width regulatingsection is composed of a lower pole layer connected to the lower corelayer, an upper pole layer connected to the upper core layer, and a gaplayer disposed between the lower pole layer and the upper pole layer, oris composed of an upper pole layer connected to the upper core layer anda gap layer disposed between the upper pole layer and the lower corelayer, and the track width regulated by the track width regulatingsection is 0.4 μm or less.

[0030] As described above, the track width regulating section, whosewidth in the track width direction is limited to the track width, isformed between the lower core layer and the upper core layer. Since thewidth of the upper core layer is larger than the track width, the volumeof the upper core layer adjacent to the leading end thereof isincreased, and magnetic saturation is adequately reduced.

[0031] In a production method which will be described later, the widthof the track width regulating section (=the track width) can be madesmaller than the resolution obtained by the wavelength of the light usedfor exposure and development of a resist.

[0032] In particular, the track width is set at 0.4 μm or less, and thisvalue is smaller than the resolution limit obtained when the i-line isused for exposure and development. More preferably, the track width isset at 0.2 μm.

[0033] Preferably, an inclined face is formed on the upper surface ofthe lower core layer extending on both sides of the track widthregulating section so as to be inclined away from the track widthregulating section in the track width direction to gradually increasethe distance from the upper core layer.

[0034] While the upper pole layer magnetically connected to the uppercore layer is formed in the track width regulating section, theabove-described configuration allows an appropriate distance between theupper pole layer and the lower core layer and thereby effectivelysuppresses write fringing.

[0035] Preferably, an inclination angle θ1 of the inclined face formedon the upper surface of the lower core layer with respect to the trackwidth direction ranges from 2° to 10°.

[0036] Preferably, the height of the track width regulating sectionranges from 2 μm to 10 μm. Within this range, an appropriate distance isensured between the lower core layer and the upper pole layer, and writefringing is suppressed. Furthermore, the height of the upper pole layeris increased, and magnetic saturation is seldom caused even when therecording density is increased. Furthermore, the track width regulatingsection can be easily formed.

[0037] Preferably, the gap layer is made of a nonmagnetic metal materialwhich can be plated. The nonmagnetic metal material may include one ormore among NiP, NiPd, NiW, NiMo, Au, Pt, Rh, Pd, Ru, and Cr.

[0038] According to a further aspect of the present invention, there isprovided with a thin-film magnetic head production method including thesteps of (a) forming a resist layer on a lower core layer and forming,in the resist layer, a groove having a predetermined width and apredetermined length from the surface opposing a recording medium in theheight direction; (b) forming, in the groove, a track width regulatingsection composed of a lower pole layer, a nonmagnetic gap layer, and anupper pole layer stacked in order or composed of a nonmagnetic gap layerand an upper pole layer stacked in order; (c) removing the resist layer;(d) limiting the width of the track width regulating section to thetrack width by etching both side faces of the track width regulatingsection in the track width direction; (e) forming an inclined face onthe upper surface of the lower core layer extending on both sides of thetrack width regulating section so as to be inclined away from the trackwidth regulating section to gradually increase the distance from theupper core layer; and (f) forming an upper core layer having a widthlarger than the track width on the track width regulating section.

[0039] As described above, the resist layer is first applied on thelower core layer, and a pattern of the track width regulating section isformed on the resist layer by exposure and development. The width of thepattern to become the track width regulating section is greatlyconcerned with the wavelength of the light used for exposure anddevelopment. For example, when the i-line (the wavelength thereof=365nm) is used, the width can be reduced to approximately 0.4 μm.

[0040] The value of 0.4 μm is the resolution limit obtained when thei-line is used, and a pattern having a width smaller than 0.4 μm cannotbe formed on the resist layer.

[0041] Accordingly, after the track width regulating section is formedin the pattern of the resist layer, the width thereof (=the track width)is further reduced by etching both side faces of the track widthregulating section in the track width direction. For this reason, forexample, when the width of the pattern formed on the resist layer isapproximately 0.4 μm that is the resolution limit obtained by the i-lineused for exposure and development, the width of the track widthregulating section can be limited to 0.4 μm or less. In this way, thepresent invention allows the width of the track width regulating section(=the track width) to be smaller than the resolution obtained by thei-line.

[0042] The production method includes the step of forming an inclinedface on the upper surface of the lower core layer extending from bothends of the track width regulating section so as to be inclined awayfrom the track width regulating section to gradually decrease thethickness of the lower core layer. This adequately prevents writefringing.

[0043] Since the upper core layer having a width larger than the trackwidth is formed on the upper pole layer constituting the track widthregulating section by, for example, flame plating, it is possible toincrease the volume of the upper core layer adjacent to the leading endthereof and to adequately reduce magnetic saturation.

[0044] Preferably, the step (d) of limiting the width of the track widthregulating section and the step (e) of forming the inclined face aresimultaneously performed by ion milling. This simplifies the productionmethod.

[0045] Preferably, the ion irradiation angle θ2 for ion milling rangesfrom 45° to 75° with respect to the direction in parallel with theheight direction of the track width regulating section. More preferably,the ion irradiation angle θ2 ranges from 55° to 70°.

[0046] The above ion irradiation angle θ2 makes it possible to reducethe track width without extremely reducing the height of the upper polelayer, as shown by the experimental result, which will be describedlater. Moreover, the inclined face can be easily formed on the uppersurface of the lower core layer by setting the ion irradiation angle 02at the above value.

[0047] Preferably, the track width to be regulated by the track widthregulating section in the above step (d) is set at 0.4 μm or less.

[0048] The track width set at 0.4 μm or less can be made smaller thanthe resolution limit obtained when the i-line is used for exposure anddevelopment of a resist. More preferably, the track width is set at 0.2μm or less.

[0049] Preferably, the inclined face formed on the upper surface of thelower core layer in the step (e) has the inclination angle θ1 rangingfrom 2° to 10° with respect to the track width direction.

[0050] By setting the ion irradiation angle θ2 for ion milling withinthe range of 45° to 75°, it is possible to make the track width 0.4 μmor less and to form the inclined face on the upper surface of the lowercore layer at the inclination angle θ1 ranging from 2° to 10° withrespect to the track width direction.

[0051] Preferably, the gap layer constituting the track width regulatingsection is formed by plating together with the pole layer. This allowsthe pole layer and the gap layer to be successively formed by plating.

[0052] Preferably, a nonmagnetic metal material to be plated to form thegap layer includes one or more among NiP, NiPd, NiW, NiMo, Au, Pt, Rh,Pd, Ru, and Cr.

[0053] Further objects, features and advantages of the present inventionwill become apparent from the following description of the preferredembodiments with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0054]FIG. 1 is a partial front view showing the structure of athin-film magnetic head according to a first embodiment of the presentinvention.

[0055]FIG. 2 is a partial sectional view of the thin-film magnetic head,taken along line II-II in FIG. 1.

[0056]FIG. 3 is a partial front view showing the structure of athin-film magnetic head according to a second embodiment of the presentinvention.

[0057]FIG. 4 is a process view showing a production method for thethin-film magnetic head according to the present invention.

[0058]FIG. 5 is a process view showing a process to be performedsubsequent to the process shown in FIG. 4.

[0059]FIG. 6 is a process view showing a process to be performedsubsequent to the process shown in FIG. 5.

[0060]FIG. 7 is a process view showing a process to be performedsubsequent to the process shown in FIG. 6.

[0061]FIG. 8 is a process view showing a process to be performedsubsequent to the process shown in FIG. 7.

[0062]FIG. 9 is a process view showing a process to be performedsubsequent to the process shown in FIG. 8.

[0063]FIG. 10 is a process view showing a process to be performedsubsequent to the process shown in FIG. 9.

[0064]FIG. 11 is a graph showing the relationship between the ionirradiation angle θ2 for ion milling and the etching rates measured at aplurality of arbitrary points.

[0065]FIG. 12 is a partial front view showing the structure of aconventional thin-film magnetic head.

[0066]FIG. 13 is a partial sectional view of the conventional thin-filmmagnetic head, taken along line XIII-XIII in FIG. 12.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0067]FIG. 1 is a partial front view showing the structure of athin-film magnetic head according to a first embodiment of the presentinvention, and FIG. 2 is a partial sectional view of the thin-filmmagnetic head, taken along line II-II in FIG. 1 and viewed from thedirection of the arrows.

[0068] A thin-film magnetic head shown in FIG. 1 is an inductive headfor recording. In the present invention, a playback head (MR head) usinga magnetoresistive effect may be placed under the inductive head.

[0069] Referring to FIGS. 1 and 2, a lower core layer 10 is made of amagnetic material such as permalloy. In a case in which a playback headis placed under the lower core layer 10, a shielding layer forprotecting a magnetoresistive element from noise may be providedseparately from the lower core layer 10, or the lower core layer 10 mayalso function as an upper shielding layer of the playback head.

[0070] As shown in FIG. 1, a track width regulating section 14 is formedon the lower core layer 10 so as to have a track width Tw. Preferably,the track width Tw is set to be 0.4 μm or less, and more preferably, tobe 0.2 μm or less.

[0071] In the present invention, the width of the track width regulatingsection 14, that is, the track width Tw, can be set to be smaller thanthe resolution obtained by the wavelength of the light to be used forexposure and development of a resist in a production method, which willbe described later. The above-described value of 0.4 μm is theresolution limit in a case in which the i-line is used to form a patternon a resist by exposure and development. According to the presentinvention, the track width Tw can be limited to be smaller than theresolution of the i-line.

[0072] In the embodiment shown in FIGS. 1 and 2, the track widthregulating section 14 has a three-layer structure composed of a lowerpole layer 11, a gap layer 15, and an upper pole layer 12. The polelayers 11 and 12 and the gap layer 15 will be described below.

[0073] As shown in FIGS. 1 and 2, the lower pole layer 11 serving as thelowermost layer of the track width regulating section 14 is formed onthe lower core layer 10 by plating, and is magnetically connected to thelower core layer 10. The lower pole layer 11 may be made of the samematerial as that of the lower core layer 10, or may be made of adifferent material. Furthermore, the lower pole layer 11 may be formedof a single-layer film or a multilayered film.

[0074] The gap layer 15, which is nonmagnetic, is formed on the lowerpole layer 11. It is preferable that the gap layer 15 be made of anonmagnetic metal material and be formed on the lower pole layer 11 byplating. Furthermore, it is preferable to select one or more among NiP,NiPd, NiW, NiMo, NiRh, Au, Pt, Rh, Pd, Ru, and Cr as the nonmagneticmetal material. The gap layer 15 may be formed of a single-layer film ora multilayered film.

[0075] The upper pole layer 12 is formed on the gap layer 15 by platingso as to be magnetically connected to an upper core layer 16, which willbe described later. The upper pole layer 11 may be made of the samematerial as that of the upper core layer 16, or may be made of adifferent material. Furthermore, the upper pole layer 16 may be formedof a single-layer film or a multilayered film.

[0076] When the gap layer 15 is made of a nonmagnetic metal material, asdescribed above, the lower pole layer 11, the gap layer 15, and theupper pole layer 12 can be successively formed by plating.

[0077] While the lower pole layer 11 and the upper pole layer 12constituting the track width regulating section 14 may be made of thesame material as that of the core layer to be magnetically connectedthereto or may be of different materials, as described above, it ispreferable, in order to improve recording density, that the lower polelayer 11 and the upper pole layer 12 opposing the gap layer 15 have ahigher saturation magnetic flux density than that of the core layer tobe magnetically connected thereto. The lower pole layer 11 and the upperpole layer 12 having such a high saturation magnetic flux density allowa recording magnetic field to be concentrated adjacent to the gap andthereby improve recording density.

[0078] As shown in FIG. 1, the track width regulating section 14 has aheight H1. For example, the thicknesses of the lower pole layer 11, thegap layer 15, and the upper pole layer 12 are set to be approximately0.4 μm, approximately 0.2 μm, and approximately 2 μm.

[0079] Preferably, the height Hi of the track width regulating section14 is set to be within the range of 2.0 μm to 3.0 μm, and morepreferably, within the range of 2.3 μm to 2.5 μm.

[0080] Within the above height range, it is possible to obtain anappropriate distance between the lower core layer 10 and the upper polelayer 12, and to thereby suppress write fringing. Moreover, since theheight and volume of the upper pole layer 12 can be increased, magneticsaturation can be suppressed at a higher recording density.

[0081] The track width regulating section 14 is produced by forming agroove in a resist layer and plating the interior of the groove withmetal materials for the magnetic layers, as will be described later.When the track width regulating section 14 has the above height, it canbe easily produced so as to allow a groove of a predetermined shape andof a predetermined size to be easily formed in the resist layer byexposure and development and so as to respond to reduction in trackwidth.

[0082] The track width regulating section 14 is formed, as shown in FIG.2, to have a predetermined length from a surface opposing a recordingmedium (an ABS) in the height direction (the Y-direction in the figure).A gap-depth-determining insulating layer 17 is formed of an organicinsulating material, such as a resist or a polyimide, on the lower corelayer 10.

[0083] The gap-depth-determining insulating layer 17 serves to regulatethe gap depth (Gd) which has a great effect on the electriccharacteristics of the thin-film magnetic head. The gap depth isdetermined by the length from the front end face of thegap-depth-determining insulating layer 17 to the ABS. As shown in FIG.2, the gap-depth-determining insulating layer 17 allows a sufficientlength of the upper pole layer 12 in the height direction (theY-direction) and a sufficient volume thereof. This prevents magneticsaturation and improves the recording characteristics.

[0084] It may be arbitrarily determined whether or not to form thegap-depth-determining insulating layer 17. When thegap-depth-determining insulating layer 17 is not provided, the gap depthis determined by the length of the track width regulating section 14 inthe height direction.

[0085] As shown in FIG. 2, an insulating layer 18 extends from the rearend of the track width regulating section 14 in the height direction.The insulating layer 18 is, for example, an inorganic insulating layermade of an inorganic material. It is preferable to select, as theinorganic material, one or more among Al₂O₃, SiN, and SiO₂.

[0086] Furthermore, it is preferable that an upper surface 18 a of theinsulating layer 18 be formed flat so as to be flush with a jointsurface, serving as a reference plane A, between the upper pole layer 12and the upper core layer 16, which will be described later.

[0087] A coil layer 19 is patterned on the insulating layer 18 in aspiral form. Since the upper surface 18 a of the insulating layer 18 isflat, the coil layer 19 can be precisely formed so that conductiveportions are formed with a reduced pitch therebetween.

[0088] Such reduction in pitch between the conductive portions makes itpossible to reduce the length of the upper core layer 16 in the heightdirection, to reduce the magnetic path length formed via the lower corelayer 10, and to improve recording characteristics.

[0089] It is preferable that the coil layer 19 be composed of aconductive material layer and a protective layer placed thereon. In thiscase, preferably, the conductive material layer is formed of anonmagnetic conductive layer having a single-layer or multilayeredstructure containing either or both Cu and Au, and the protective layeris formed of a nonmagnetic conductive layer having a single-layer ormultilayered structure containing one or more selected among elementsNi, NiP, Pd, Pt, B, and Au.

[0090] Before an organic insulating layer 20 is formed on the patternedcoil layer 19, the coil layer 19 is sometimes exposed to the atmosphere.In this case, the protective layer serves to prevent the coil layer 19from being oxidized.

[0091] As shown in FIG. 2, the organic insulating layer 20 made of anorganic material, such as a resist or a polyimide, is formed on the coillayer 19, and the upper core layer 16 made of a magnetic material, suchas permalloy, is formed on the organic insulating layer 20 by flameplating or by another method.

[0092] A leading end portion 16a of the upper core layer 16 is formed onthe upper pole layer 12 so as to be magnetically connected thereto, anda base end portion 16 b is formed on a connecting magnetic layer(backgap layer) 21 made of a magnetic material on the lower core layer10 so as to be magnetically connected thereto. In the present invention,the connecting magnetic layer 21 may be omitted. In this case, the baseend portion 16 b of the upper core layer 16 is in direct contact withthe lower core layer 10.

[0093] In the inductive head shown in FIGS. 1 and 2, when a recordingcurrent is applied to the coil layer 19, a recording magnetic field isinduced in the lower core layer 10 and the upper core layer 16, and aleakage magnetic field is produced between the lower pole layer 11 andthe upper pole layer 12 opposing via the gap layer 15 in the track widthregulating section 14. In response to this leakage magnetic field, amagnetic signal is recorded on a recording medium such as a hard disk.

[0094] The present invention provides the inductive head with theconfiguration shown in FIG. 1 in order to reduce the track width forfurther increase in recording density, to adequately prevent writefringing, and to reduce magnetic saturation.

[0095] In the inductive head shown in FIG. 1, the track width regulatingsection 14, in which the width in the track width direction (theX-direction) is limited to the track width Tw, is formed between thelower core layer 10 and the upper core layer 16.

[0096] Since the width of the track width regulating section 14 is setto be smaller than the resolution obtained by the wavelength of thelight used for exposure and development of the resist, as describedabove, reduction in track width can be adequately achieved. Morespecifically, the track width Tw can be limited to 0.4 μm or less, morepreferably, to 0.2 μm or less.

[0097] In the present invention, the upper core layer 16 has a width T1in the track width direction (the X-direction), as shown in FIG. 1. Thewidth T1 is set to be larger than the track width Tw. For this reason,it is possible to increase the volume of the upper core layer 16adjacent to the leading end portion 16 a and to more adequately reducemagnetic saturation.

[0098] As shown in FIG. 1, inclined faces 10 a are formed on the uppersurface of the lower core layer 10 extending from both sides of thetrack width regulating section 14 so as to be inclined in directionsaway from the track width regulating section 14.

[0099] Since the lower core layer 10 and the upper pole layer 12constituting the track width regulating section 14 are properlyseparated by the inclined faces 10 a, a leakage magnetic field producedfrom the upper pole layer 12 is prevented from protruding from the trackwidth Tw by the influence of the width of the lower core layer 10. Thissuppresses so-called write fringing.

[0100] Preferably, an inclination angle θ1 formed by a parallel lineextending in parallel with the track width direction (the X-direction inthe figure) and the inclined face 10 a ranges from 2° to 10°.

[0101] When the inclination angle θ1 of the inclined face 10 a is lessthan 2°, a leakage magnetic flux is prone to be produced between thelower core layer 10 and the upper pole layer 12, and the effect ofsuppressing write fringing cannot be anticipated.

[0102] An inclination angle 01 of the inclined face 10 a larger than 10°is effective in suppressing write fringing. However, in a case in whichthe lower core layer 10 also functions as a shielding layer of amagnetoresistive element (not shown), when the inclination angle θ1exceeds 10°, the thickness of the lower core layer 10, in particular,adjacent to both sides thereof, is decreased, or the width itself of thelower core layer 10 in the track width direction (the X-direction in thefigure) is decreased. This impairs the function of the lower core layer10 as a shielding layer of the magnetoresistive element.

[0103] As shown in FIG. 1, a protuberance 10 c may be formed on theupper surface of the lower core layer 10 so as to extend in theZ-direction in the figure. In this case, the upper surface of theprotuberance 10 c is joined to the base end of the track widthregulating section 14. Preferably, inclined faces 10 b are formed on theupper surface of the lower core layer 10 extending from the base end ofthe protuberance 10 c so as to be inclined in directions away from thetrack width regulating direction 14. While the protuberance 10 c shownin FIG. 1 is shaped like a rectangle having a width equal to the trackwidth Tw, it may be formed in another shape. For example, theprotuberance 10 c may be shaped like a trapezoid having the uppersurface of the track width Tw and both side faces inclined so that thewidth gradually increases toward the lower core layer 10 (in thedirection opposite from the Z-direction in the figure).

[0104] In the present invention, the lower core layer 10 need not beprovided with the inclined faces 10 a or 10 b, and the upper surface ofthe lower core layer 10 may be formed in parallel with the track widthdirection (the X-direction). In this case, however, the above-describedwrite fringing is more likely to occur, compared with a case in whichthe inclined faces 10 a or 10 b are formed.

[0105] The present invention provides the advantages of adequatelyreducing the track width and effectively suppressing magnetic saturationeven when the upper surface of the lower core layer 10 is in parallelwith the track width direction, and this differs from the conventionalinductive head. When the lower core layer 10 has the protuberance 10 c,the lower core layer 10 and the upper pole layer 12 can be separated,and therefore, write fringing can be effectively suppressed without theinclined faces 10 b.

[0106]FIG. 3 is a partial front view showing the structure of athin-film magnetic head according to a second embodiment of the presentinvention.

[0107] This embodiment is similar to the first embodiment shown in FIG.1 except for the layer structure of a track width regulating section 14.

[0108] As shown in FIG. 3, the track width regulating section 14 iscomposed of two layers, a gap layer 15 and an upper pole layer 12.

[0109] Inclined faces 10a are formed on the upper surface of a lowercore layer 10 extending from the base end of the gap layer 15 so as tobe inclined in directions away from the track width regulating section14. This allows write fringing to be adequately suppressed.

[0110] A protuberance 10 c extending in the Z-direction in the figuremay also be formed on the upper surface of the lower core layer 10, andthe upper surface of the protuberance 10 c may be joined to the base endof the track width regulating section 14. Preferably, inclined faces lobare formed on the upper surface of the lower core layer 10 extendingfrom the base end of the protuberance 10 c so as to be inclined indirections away from the track width regulating section 14. This allowswrite fringing to be adequately suppressed.

[0111] FIGS. 4 to 10 are process views showing a production method forthe thin-film magnetic head (inductive head) of the present inventionshown in FIGS. 1 and 2. FIGS. 4 to 7 are partial front views, and FIGS.8 to 10 are partial longitudinal sectional views.

[0112] In a case in which a gap-depth-determining insulating layer 17 isformed, as shown in FIG. 8 and subsequent figures, it must be formed ona lower core layer 10 beforehand.

[0113] Referring to FIG. 4, first, a resist layer 30 having a thicknessH2 is applied on the lower core layer 10.

[0114] Then, a groove 30 a is patterned by exposure and development inthe resist layer 30 so as to form a track width regulating section 14therein. As shown in FIG. 4, the groove 30 a has a width T2 in the trackwidth direction (the X-direction) and a predetermined length in theheight direction (the Y-direction).

[0115] For example, when the i-line is used for exposure anddevelopment, the width T2 of the groove 30 a formed in the resist layer30 can be reduced to approximately 0.4 μm. The value of 0.4 μm is theresolution limit obtained by the i-line, and the width T2 of the groove30 a cannot be smaller than the value.

[0116] In order to improve resolution, it is only necessary to use lighthaving a shorter wavelength during exposure and development. In order tomake the resolution higher than that when the i-line is used, an excimerlaser may be used. When the excimer laser is used, the width T2 of thegroove 30 a formed in the resist layer 30 can be reduced toapproximately 0.3 μm.

[0117] Subsequently, the track width regulating section 14 is formed inthe groove 30 a of the resist layer 30, as shown in FIG. 5. In theembodiment of the present invention, the track width regulating section14 has a multilayered structure in which a lower pole layer 11, a gaplayer 15, and an upper pole layer 12 are stacked from the bottom in thatorder. The lower pole layer 11 is formed by electroplating or by anothermethod so as to be magnetically connected to the lower core layer 10.The upper pole layer 12 is formed by electroplating or by another methodso as to be magnetically connected to an upper core layer 16.

[0118] In the present invention, it is preferable that the gap layer 15be formed together with the pole layers 11 and 12 by plating. Thisallows the pole layers 11 and 12 and the gap layer 15 to be successivelyformed by plating.

[0119] As a nonmagnetic metal material to be used for plating forforming the gap layer 15, it is preferable to select one or more amongNiP, NiPd, NiW, NiMo, Au, Pt, Rh, Pd, Ru, and Cr.

[0120] The track width regulating section 14 need not have a three-layerstructure composed of the lower pole layer 11, the gap layer 15, and theupper pole layer 12, and may have, for example, a two-layer structurecomposed of the gap layer 15 and the upper pole layer 12.

[0121] As shown in FIG. 5, the track width regulating section 14 has aheight H3. The height H3 is set to be equal to or slightly smaller thanthe thickness H2 of the resist layer 30.

[0122] The height H3 is also set to be larger than the height H1 of thetrack width regulating section 14 shown in FIG. 1. That is, the heightH2 itself of the resist layer 30 for regulating the height of the trackwidth regulating section 14 is set beforehand to be larger than theheight H1 in the process shown in FIG. 4.

[0123] The height H3 is determined in consideration of the height Hi ofthe track width regulating section 14, the amount of polishing in apolishing process using chemical-mechanical polishing (CMP) shown inFIG. 7, and the like.

[0124] The height of the track width regulating section 14 is reduced byapproximately 1 μm in the polishing process, and is also reduced in anion milling process shown in FIG. 6.

[0125] As described above, in the present invention, it is preferablethat the height Hi of the track width regulating section 14 (see FIG. 1)after production be within the range of 2 μm to 3 μm, more preferably,within the range of 2.3 μm to 2.5 μm. In order to ensure the aboveheight H1, it is preferable that the height H3 of the track widthregulating section 14 shown in FIG. 5 be set to be within the range of3.5 μm to 5.0 μm, more preferably, within the range of 4.0 μm to 4.2 μm,in consideration of the polishing and ion milling processes.

[0126] After the track width regulating section 14 is formed in thegroove 30 a of the resist layer 30 in the above-described manner, aconnecting magnetic layer 21 shown in FIG. 2 is formed.

[0127] The connecting magnetic layer 21 is formed on the lower corelayer 10 by removing the resist layer 30 after the process shown in FIG.5, forming a resist layer again, forming a pattern of the connectingmagnetic layer 21 on the resist layer, and plating the pattern with amagnetic material.

[0128]FIG. 6 shows a state in which the resist layer for forming theconnecting magnetic layer 21 is removed.

[0129] As shown in FIG. 6, only the track width regulating section 14stands adjacent to the ABS on the lower core layer 10. In this state,the width of the track width regulating section 14 is further reduced byetching both side faces 14 a thereof in the track width direction (theX-direction in the figure).

[0130] In the present invention, both side faces 14 a of the track widthregulating section 14 are etched by, for example, ion milling using anAr (argon) gas neutralized and ionized.

[0131] As shown in FIG. 6, ion milling is performed from the obliquedirections (the directions of the arrows B and C). When ions are appliedfrom these directions, both side faces 14 a of the track widthregulating section 14 are gradually etched by a physical action, therebyreducing the width of the track width regulating section 14.

[0132] As described above, it is preferable that the gap layer 15constituting the track width regulating section 14 be made of anonmagnetic metal material by plating. In this case, since the gap layer15 and the pole layers 11 and 12 are etched at nearly the same millingrate, both side faces 14 a of the track width regulating section 14 areadequately etched in the same planar shape.

[0133] The width of the track width regulating section 14 is regulatedas the track width Tw. According to the present invention, the trackwidth Tw can be made smaller than the resolution limit obtained by thewavelength of the light used during exposure and development of theresist.

[0134] That is, while the groove 30 a is formed in a portion of theresist layer 30, where the track width regulating section 14 is to beformed, in the process shown in FIG. 4, the width T2 of the groove 30 ais equal to at least the resolution limit obtained by the wavelength ofthe light used during exposure and development, and cannot be furtherreduced.

[0135] Therefore, while the track width regulating section 14 is formedin the groove 30 a of the resist layer 30 so as to have the width T2(see FIG. 6), in the present invention, the width of the track widthregulating section 14 can be made smaller than T2 by etching both sidefaces 14 thereof by ion milling or by another method. In other words,the track width Tw of the track width regulating section 14 can be madesmaller than the resolution limit obtained by the wavelength of thelight used during exposure and development of the resist (see FIG. 7).

[0136] For example, in a case in which the i-line is used for exposureand development of the resist layer 30, the width T2 of the groove 30 ato be formed in the resist layer 30 is approximately 0.4 μm at aminimum. In the present invention, the width of the track widthregulating section 14 (=the track width Tw) can be reduced to 0.4 μm orless by etching both side faces 14 a of the track width regulatingsection 14 by ion milling in the process shown in FIG. 6. Furthermore,the track width Tw can be reduced to 0.2 μm or less by controlling theion milling period and the ion irradiation angle.

[0137] When both side faces 14 a of the track width regulating section14 have been etched by ion milling, the width of the track widthregulating section 14 is set as the track width Tw, as shown in FIG. 7.Simultaneously, the upper surface of the lower core layer 10 extendingfrom both sides of the track width regulating section 14 is alsoobliquely etched by ion milling, whereby inclined faces 10 a are formedthereon.

[0138] In this way, two processes, the process of limiting the width ofthe track width regulating section 14 to the track width Tw by etchingboth side faces 14 a of the track width regulating section 14 and theprocess of forming the inclined faces 10 a on the upper surface of thelower core layer 10, can be simultaneously performed by ion milling. Forexample, in order to prevent magnetic powders produced by etching thelower core layer 10 from adhering thereto again and to set theinclination angle θ1 of the inclined faces 10 a formed on the lower corelayer 10 to be within a predetermined range (the above-described rangeof 2° to 10°), it is necessary to appropriately set the ion irradiationangle θ2 during ion milling (the angle of irradiation of ions withrespect to the height direction (the Z-direction) of the track widthregulating section 14).

[0139] In the present invention, it is preferable that the ionirradiation angle θ2 be set to range from 45° to 75°.

[0140] According to the experimental results, which will be describedlater, when the ion irradiation angle θ2 ranges from 45° to 75°, theetching rate of both side faces of the track width regulating section 14is a positive value. This makes it possible to properly etch both sidefaces of the track width regulating section 14 and to limit the trackwidth Tw to 0.4 μm or less.

[0141] On the other hand, while the upper surface of the upper polelayer 12 (that is, the upper surface of the track width regulatingsection 14) is etched by the ion irradiation, the etching rate thereofis highest when the ion irradiation angle θ2 is within the range of 40°to 45°. Therefore, the etching rate can be decreased by setting the ionirradiation angle θ2 to be 45° or more, and the height of the trackwidth regulating section 14 can be prevented from being excessivelyreduced.

[0142] In the case of the above ion irradiation angle θ2, since theetching rate at joint portions D between the lower core layer 10 and thetrack width regulating section 14 is a positive value, the jointportions D are adequately etched, and there is no fear that the uppersurface of the lower core layer 10 will raised due to magnetic powdersadhering again thereto during ion milling.

[0143] As described above, the conventional thin-film magnetic head (seeFIG. 12) requires the process of etching the surfaces of the gap layer 7protruding from the track width Tw and the lower core layer 1 formedthereunder by ion milling, and the process of removing the substancesadhering again to the upper core layer 3 due to ion milling. Incontrast, since the track width regulating section 14 of the presentinvention has a three plated layer structure including the gap layer 15and has a protuberance, the above ion milling is unnecessary. For thisreason, the substances are prevented from adhering again due to ionmilling.

[0144] In the present invention, even when the width of the track widthregulating section 14 in the track width direction is made slightlylarger than a predetermined width before the ion milling process (FIG.5), the track width Tw can be easily caused to fall within apredetermined width range by correcting the amount of etching of bothside faces 14 a of the track width regulating section 14.

[0145] In the process shown in FIG. 4, before the resist layer 30 isformed, an underplate layer is formed on the upper surface of the lowercore layer 10 in order to form the track width regulating section 14thereon. In the process shown in FIG. 6, the underplate layer, excludinga portion disposed under the track width regulating section 14, isadequately removed by ion milling. Therefore, it is unnecessary toconsider a process of removing the underplate layer.

[0146] As described above, the track width Tw of the track widthregulating section 14 can be made 0.4 μm or less, more preferably, 0.2μm or less, by performing ion milling at the ion irradiation angle θ2.Moreover, the inclination angle θ1 of the inclined faces 10 a formed onthe upper surface of the lower core layer 10 can be controlled so as tobe within the range of 2° to 10°.

[0147] In particular, when the ion irradiation angle θ2 is within therange of 55° to 70°, as shown by the experimental results, which will bedescribed later, it is possible to adjust the etching rate at both sidefaces of the track width regulating section 14, the etching rate on theupper surface of the upper pole layer 12, and the etching rate at thejoint portions D between the lower core layer 10 and the track widthregulating section 14 so that the etching rates are within theirrespective appropriate ranges, and to easily set the track width Tw ofthe track width regulating section 14 and the inclination angle θ1 ofthe inclined surfaces 10 a within the above predetermined ranges withoutany influence of re-adhesion due to ion milling.

[0148] While ion milling is performed with the ion irradiation angle θ2fixed at an angle within the range of 45° to 75°, since the appropriateranges of the etching rate for setting the track width Tw within apredetermined range and the etching rate for forming the inclined faces10 a on the upper surface of the lower core layer 10 are different, forexample, it may be possible to reduce the track width Tw by etching bothside faces 14 a of the track width regulating section 14 with the ionirradiation angle θ2 set within the range of 60° to 75°, and to thenform the inclined faces 10 a having an appropriate inclination angle θ1on the upper surface of the lower core layer 10 with the ion irradiationangle θ2 changed to the range of 45° to 60°.

[0149] Since the joint portions D between the lower core layer 10 andthe track width regulating section 14 can be properly etched as long asthe ion irradiation angle θ2 is within the above range, the protuberance10 c shown in FIGS. 1 and 3 can be formed on the lower core layer 10.Alternatively, the protuberance 10 c may be formed by etching only theupper surface of the lower core layer 10 by ion milling, in which theion irradiation angle with respect to the lower core layer 10 issubstantially vertical (0° to approximately 15°), before the processshown in FIG. 6 of etching both side faces 14 a of the track widthregulating section 14, and the ion milling process shown in FIGS. 6 and7 may then be performed.

[0150] Thereby, the protuberance 10 c is formed on the lower core layer10, as shown in FIGS. 1 and 3, and the inclined faces 10 b are formed onthe upper surface of the lower core layer 10 extending from the base endof the protuberance 10 c so as to be inclined to gradually reduce thethickness of the lower core layer 10 in directions away from the trackwidth regulating section 14.

[0151] Next, the lower core layer 10 is covered with an insulating layer18, as shown in FIG. 8. In this case, the track width regulating section14 and the connecting magnetic layer 21 are also covered with theinsulating layer 18.

[0152] In the present invention, the insulating layer 18 is made of aninorganic material by sputtering. It is preferable to select, as theinorganic material, one or more among Al₂O₃, SiN, and SiO₂.

[0153] As shown in FIG. 8, the surface of the insulating layer 18 isground to the line D-D, for example, by CMP so that the surface of thetrack width regulating section 14 is exposed. An upper surface 18 a ofthe insulating layer 18 is thereby formed to be flat and to be flushwith a surface 14 b of the track width regulating section 14, as shownin FIG. 9. A surface 21 a of the connecting magnetic layer 21 is alsoexposed by the above polishing process using CMP.

[0154] As described above, the height of the track width regulatingsection 14 is reduced by approximately 1 μm by the polishing process.After this process, the height H1 (see FIG. 1) of the track widthregulating section 14 is within the range of 2 μm to 3 μm.

[0155] Subsequently, a coil layer 19 is patterned on the insulatinglayer 18 in a spiral form, as shown in FIG. 9. Since the surface 18a ofthe insulating layer 18 is flat, as described above, the coil layer 19can be formed precisely. This makes it possible to form conductiveportions with a smaller pitch therebetween.

[0156] As shown in FIG. 10, the coil layer 19 is covered with an organicinsulating layer 20 made of an organic material, such as a resist or apolyimide, and an upper core layer 16 is patterned on the organicinsulating layer 20 by an existing method such as flame plating. Aleading end portion 16 a of the upper core layer 16 is in contact withthe track width regulating section 14, and a base end portion 16 bthereof is in magnetic contact with the connecting magnetic layer 21 onthe lower core layer 10.

[0157] The width of the leading end portion 16 a of the upper core layer16 in the track width direction (the X-direction) is set at T1, which islarger than the track width Tw, as shown in FIGS. 1 and 3. The leadingend portion 16 a thus has a width T1 which is larger than the trackwidth Tw because the track width Tw is already determined by the widthof the upper pole layer 12 separate from the upper core layer 16.

[0158] Since the width of the leading end portion 16 a of the upper corelayer 16 is thus larger than the track width Tw, it is possible to formthe upper core layer 16 with a higher pattern accuracy than previously(that is, compared with a case in which the width of the leading endportion 16 a is limited to the track width Tw). Furthermore, since thewidth T1 of the leading end portion 16 a of the upper core layer 16 canbe increased, the volume of the upper core layer 16 can also beincreased and magnetic saturation can be adequately suppressed.

[0159] In the present invention, examinations were made of therelationship between the ion irradiation angle and the etching rate atan arbitrary point during ion milling performed in the process shown inFIG. 6.

[0160] In an experiment, first, an inductive head having a shape shownin FIG. 6 was produced. In this case, the width T2 of a track widthregulating section 14 in the track width direction (the X-direction) wasset to be within the range of 0.55 μm to 0.6 μm. The height H3 of thetrack width regulating section 14 was set to be within the range of 4 μmto 4.2 μm.

[0161] The etching rate on both side faces of the track width regulatingsection 14, the etching rate on the upper surface of an upper pole layer12, and the etching rate at joint portions (portions indicated by theletter D in FIG. 6) between a lower core layer 10 and the track widthregulating section 14 were measured while changing the ion irradiationangle θ2 (see FIG. 6). The results of the experiment are shown in FIG.11.

[0162] As shown in FIG. 11, the etching rate E on both side faces of thetrack width regulating section 14 linearly increases as the ionirradiation angle θ2 increases.

[0163]FIG. 11 shows that the etching rate E has a negative value whenthe ion irradiation angle θ2 is within the range of 0° to approximately40°. This means that magnetic powders produced by ion milling adhereagain. Within the above range of the ion irradiation angle θ2, magneticpowders chipped off the lower core layer 10 and the like adhere to bothside faces of the track width regulating section 14, thereby increasingthe width T2 of the track width regulating section 14 in the track widthdirection.

[0164] That is, in order to reduce the width T2 of the track widthregulating section 14 and to thereby ensure a track width Tw of 0.4 μmor less, the etching rate E must have at least a positive value.

[0165] The etching rate G on the upper surface of the upper pole layer12 is highest when the ion irradiation angle θ2 is approximately 40° to45°, and gradually decreases when the ion irradiation angle θ2 furtherincreases.

[0166] As shown in FIG. 11, the etching rate G has a positive valueregardless of the ion irradiation angle θ2. That is, the upper surfaceof the upper pole layer 12 is etched by ion milling, and the height ofthe upper pole layer 12 is reduced. However, it is preferable that theheight of the upper pole layer 12 not be reduced as much as possible.This is because the volume of the upper pole layer 12 decreases as theheight thereof decreases, and magnetic saturation is easily caused at ahigher recording density. Therefore, it is preferable that the etchingrate G have as small a positive value as possible.

[0167] The etching rate F at the joint portion D of the lower core layer10 linearly decreases as the ion irradiation angle θ2 increases. Inparticular, when the ion irradiation angle θ2 exceeds approximately 75°,the etching rate F is a negative value. This means that magnetic powdersproduced by ion milling adhere again.

[0168] It is satisfactory as long as at least the etching rate F is nota negative value. When the etching rate F is a negative value, magneticpowders removed from the track width regulating section 14 and the likeby etching adhere to the joint portions D of the lower core layer 10,and the joint portions D are raised. Since this shortens the distancebetween the lower core layer 10 and the upper pole layer 12, writefringing is worsened.

[0169] From the above point of view, the ion irradiation angle θ2 is setto be within the range of 45° to 75°. Within this range, the etchingrate E on both side faces of the track width regulating section 14 is alarge positive value, as shown in FIG. 11, and therefore, the width T2of the track width regulating section 14 in the track width directioncan be reduced. In the present invention, it has been confirmed that thetrack width Tw can be reduced to 0.2 μm or less.

[0170] In contrast, when the ion irradiation angle θ2 is within theabove range, the etching rate G on the upper surface of the upper polelayer 12 is a positive value, but tends to decrease. When ion millingwas completed, the height of the track width regulating section 14measured approximately 3.3 μm to 3.5 μm.

[0171] When the ion irradiation angle θ2 is within the above range, theetching rate F at the joint portions D of the lower core layer 12 showsa positive value, and re-adhesion of magnetic powders due to ion millingis prevented. Therefore, it is possible to form the protuberance 10 cshown in FIG. 1 in the lower core layer 10.

[0172] The above ion irradiation angle θ2 allows the inclination angleθ1 of the inclined faces 10 a formed on the upper surface of the lowercore layer 10 to fall within the range of 2° to 10°.

[0173] It is more preferable that the ion irradiation angle θ2 be withinthe range of 55° to 70°. This range makes it possible to adequatelyreduce the etching rate on the upper surface of the upper pole layer 12,to make the etching rate on both side faces of the track widthregulating section 14 a positive large value, and to reliably make theetching rate at the joint portions D of the lower core layer 10 apositive value.

[0174] While the present invention has been described with reference towhat are presently considered to be the preferred embodiments, it is tobe understood that the invention is not limited to the disclosedembodiments. On the contrary, the invention is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims. The scope of the following claims is to beaccorded the broadest interpretation so as to encompass all suchmodifications and equivalent structures and functions.

What is claimed is:
 1. A thin-film magnetic head comprising: upper andlower core layers; and a track width regulating section disposed betweensaid upper and lower core layers so as to have a width shorter thanthose of said upper and lower core layers, wherein said track widthregulating section is composed of a lower pole layer connected to saidlower core layer, an upper pole layer connected to said upper corelayer, and a gap layer disposed between said lower pole layer and saidupper pole layer, or is composed of an upper pole layer connected tosaid upper core layer and a gap layer disposed between said upper polelayer and said lower core layer, and wherein an inclined face is formedon the upper surface of said lower core layer extending on both sides ofsaid track width regulating section so as to be inclined away from saidtrack width regulating section in the track width direction in order togradually increase the distance from said upper core layer.
 2. Athin-film magnetic head according to claim 1, wherein the width of saidtrack width regulating section is 0.4 μm or less.
 3. A thin-filmmagnetic head according to claim 2, wherein the width is 0.2 μm or less.4. A thin-film magnetic head according to claim 1, wherein aninclination angle θ1 of said inclined face formed on the upper surfaceof said lower core layer with respect to the track width direction iswithin the range of 2° to 10°.
 5. A thin-film magnetic head comprising:upper and lower core layers; and a track width regulating sectiondisposed between said upper and lower core layers so as to have a widthshorter than those of said upper and lower core layers, wherein saidtrack width regulating section is composed of a lower pole layerconnected to said lower core layer, an upper pole layer connected tosaid upper core layer, and a gap layer disposed between said lower polelayer and said upper pole layer, or is composed of an upper pole layerconnected to said upper core layer and a gap layer disposed between saidupper pole layer and said lower core layer, and wherein the width ofsaid track width regulating section is 0.4 μm or less.
 6. A thin-filmmagnetic head according to claim 5, wherein the width is 0.2 μm or less.7. A thin-film magnetic head according to claim 5, wherein an inclinedface is formed on the upper surface of said lower core layer extendingon both sides of said track width regulating section so as to beinclined away from said track width regulating section in the trackwidth direction to gradually increase the distance from said upper corelayer.
 8. A thin-film magnetic head according to claim 7, wherein aninclination angle θ1 of said inclined face formed on the upper surfaceof said lower core layer with respect to the track width direction iswithin the range of 2° to 10°.
 9. A thin-film magnetic head according toclaim 1, wherein the height of said track width regulating section iswithin the range of 2 μm to 3 μm.
 10. A thin-film magnetic headaccording to claim 1, wherein said gap layer is made of a nonmagneticmetal material which can be plated.
 11. A thin-film magnetic headaccording to claim 10, wherein said nonmagnetic metal material includesone or more selected among NiP, NiPd, NiW, NiMo, Au, Pt, Rh, Pd, Ru, andCr.
 12. A thin-film magnetic head according to claim 5, wherein theheight of said track width regulating section is within the range of 2μm to 3 μm.
 13. A thin-film magnetic head according to claim 5, whereinsaid gap layer is made of a nonmagnetic metal material which can beplated.
 14. A thin-film magnetic head according to claim 5, wherein saidnonmagnetic metal material includes one or more selected among NiP,NiPd, NiW, NiMo, Au, Pt, Rh, Pd, Ru, and Cr.
 15. A thin-film magnetichead production method comprising the steps of: (a) forming a resistlayer on a lower core layer and forming, in said resist layer, a groovehaving a predetermined width and a predetermined length from the surfaceopposing a recording medium in the height direction; (b) forming, insaid groove, a track width regulating section composed of a lower polelayer, a nonmagnetic gap layer, and an upper pole layer stacked in orderor composed of a nonmagnetic gap layer and an upper pole layer stackedin order; (c) removing said resist layer; (d) limiting the width of saidtrack width regulating section to the track width by etching both sidefaces of said track width regulating section in the track widthdirection; (e) forming an inclined face on the upper surface of saidlower core layer extending on both sides of said track width regulatingsection so as to be inclined away from said track width regulatingsection to gradually increase the distance from said upper core layer;and (f) forming an upper core layer having a width larger than the trackwidth on said track width regulating section.
 16. A thin-film magnetichead production method according to claim 15, wherein said step (d) oflimiting the width of said track width regulating section and said step(e) of forming said inclined face are simultaneously performed by ionmilling.
 17. A thin-film magnetic head production method according toclaim 16, wherein an ion irradiation angle θ2 for ion milling rangesfrom 45° to 75° with respect to the direction in parallel with theheight direction of said track width regulating section.
 18. A thin-filmmagnetic head production method according to claim 17, wherein the ionirradiation angle θ2 ranges from 55° to 70°.
 19. A thin-film magnetichead production method according to claim 15, wherein the track width tobe regulated by said track width regulating section in said step (d) is0.4 μm or less.
 20. A thin-film magnetic head production methodaccording to claim 19, wherein the track width is 0.2 μm or less.
 21. Athin-film magnetic head production method according to claim 15, whereinsaid inclined face formed on the upper surface of said lower core layerin said step (e) has an inclination angle θ1 ranging from 2° to 10° withrespect to the track width direction.
 22. A thin-film magnetic headproduction method according to claim 15, wherein said gap layerconstituting said track width regulating section is formed by platingtogether with said pole layer.
 23. A thin-film magnetic head productionmethod according to claim 22, wherein a nonmagnetic metal material to beplated to form said gap layer includes one or more selected among NiP,NiPd, NiW, NiMo, Au, Pt, Rh, Pd, Ru, and Cr.